Method of and apparatus for making electric steel



March 31 1925.

J. GALJUQ METHOD OF AND APPARATUS FOR MAKlNG ELBCTRYC STEM;

Filed April .28. 1920 2 Sneets Shmi; l

WIYWESa INV NTQR. I may W mzzw A TTORNEYS.

INVENTOR.

ATTORNEYS.

2 Sheets-Sheet 2 J. W. GALVIN METHOD OF AND APPARATUS FOR MAKING ELECTRTC STEEL Filed April 28 March 31.1925.

Patented Mar. 31, 1925,.

UNITED STATES J W. GALVIN, OE SPRINGFIELD, OHIO,

ASSIGNOR OF ONE-HALF T0 JQHN GAKLWN,

0F LIMA, GHIO.

METHGD OF AND APPARATUS EQR MAKING ELEG'ERIC fi ll'illlr.

hpplication filed April as,

Be it known that 1, JAMES W. GALVIN, a citizen of the United States, residing at Springfield, in the county of Clarlrand State of Ohio, have invented certain new and useful Improvements in Methods of and Apparatus for Making Electric Steel, of which the following is a specification.

This invention relates to an improved method of and apparatus for making electric steel.

()ne of the principal objects of my invcntion. is the provision of an improved method of and apparatus for producing steel in electric furnaces by virtue of which I am enabled to not only produce a elven ,quan tity of steel in less time and with much less power than is ordinarily required, but also to roduce a product which is superior.

nether of the principal objects of my invention is to eliminatecertain of the difficulties and disadvantages incidentto the operation of standard electric melting fur-v naces.

My invention also contemplates the increase of the rated outputof a standard furnace, about two to four times.

The foregoing, together with such other objects asniay hereinafter appear, or are incident to my invention, willfbe best understood from a brief description of stand-1 and practice, when taken in connection with the drawing, forming a part'of this specificat'ion, and of which Figure 1 is a cross section through a standard tilting electric furnace, suchas' :1 Moore arc furnace, of three time rated capacity; Figure 2 is a cross section through the same furnace as modified in accordance with my invention; Figure 3 is a' section illustrating the furnace of Figure 2, tilted to increase'its capacity; and Figure 4.- ,is a

. cross section illustrating how the capacit of a standard furnace may increased.

The structure be still further shown in Figure 1, 'although specifically showing the Moore are furnace, may be taken as atypical illustration of the standard practice in the art. The bottom of the furnace is protected bya lining T'of refractory material'such as silica, such lining being built u siderable depth so that the heart 8 is; latively shallow and may be character'lled as being dish-shaped. The side wallsare to con- 1920. Serial No. 377,137.

provided with optthings for tapping the metal, such openings being closed by the doors 9. The electrodes are represented at IOzmd it will be understood that they are operated automatically in the usual mannerso as to initially draw the are and reestablish it when broken. Assuming that the furnace has a three ton rated capacity, the customary operation is as follows:

Three tons of scrap are charged into the furnace. A small amount of pig iron or other carbonizer may be included in this charge or added thereto during the melting and in some cases in order to secure the proper'chemical composition other elements such as manganese ore, ferromanganesc,

ferro silicon, and the like may he added during the melting. When the current is first I turned on, the electrodes are advanced un til they engage the scrapv and then they are slightly retracted, drawing the arc. The

scrap immediately adjacent to the electrodes 1s melted and the molten. metalsinlrs to the their automatic operatidmfollow down horing holes in he scrap. it will be readily bottom, and the electrodes, by virtue of understood hy thoseskilled in the art that during this period, the arc will he frequently broken and the electrodes automatically shifted to reestablish the arc, as a result of which the load fluctuations are very heavy. As the melting continues, the molten metal oollectsin a bath and the slag floating on the bath frequently breaks the arc and the electrodes are automatically 1 lowered to re establish it and the ends t ereof immersed in the slag. In fact, it is very common that the electrodes remain immersed in the slag after the arc has been reestablished. This is detrimental, for the reason that the slag, by virtue of its higher resistance, immediately begins to boil violently and eats oil the ends of the electrodes, as a result of which the metal absorbs the carbon, and also becausethe are istoo short. It will be understood that'th'e heavy load fluctuations above ,referred to take place during thisv period as well. the entire charge is'dra'wn ofi into the ladle as one batch, the furnace is recharged and the operation repeated.

After the'charge is melted Another difficulty encountered in the op? 'quentl it is 'foun scrap owing to the interstices:

:"eration of this type of furnace is that fretween pieces of scrap hcing so large to thereto a fresh charge, so that prevent the formation of a suitable arc. It is furthermore commonly necessary, because of the shape of the hearth, to pull "-hc scrap into the bath of metal by using a hook or bar.

In addition to the roregoing, the power costs are high because the current and time requirements are relatively large. To ov n come this and. other disadvantages, 1 pro pose, briefly considered, the leave a gortion of the molten metal in the furnace, when drawing ofi a batch during a run, to add .ter

will absorb heat from the molten met 7 maining in the furnace and the contents of the furnace will constitute a of great conductivity. in other Words, enough. molten metal is left to give the mass oi;

7 pieces of the succeeding charge conductivity to sustain the flow of current or are be seen such charge and the superadjacent electrode means. This materially cuts down the power and the time required and secures other advantages which will appear. Such a process could not be carried out successfully in the standard furnace; but l'havc found that the furnace may be modified so as to carry out this process.

Ihave discovered that the lining 7 used in standard practice is more than twice as thick as is necessary for safety and proper radiation. This allows me, even While remining the standard construction and configuration in other respects, "to construct the lining as shown in Figure 2,.so to produce a cup shaped /hearth 8, of dean cupped or deegnnbuhded howl profile, and

with outward ire toward the furnace sides sufficiently pronounced to cause unmolten material to gravitate even into the relatively narrow initial central pool or of: molten metal on the hearth, and toxin therewith a mass of greater conductivity for sustaining the are. The capacity of the furnace greatly increased; and it may he ther increased, iii desired, by sidewalls of the lining to a l By building the sidewalls upon on.

ample, in Figures 2, o and l, the right hand, the capacity of the furnace may he still iurther increased will herein-a appear. When the sides the lining are thus built up higher on one side than on the other," I prefer to corresnondingly brick up the respectlve sides of the furnace wall proper, as shown in F gurc'il, providing a tap hole9' in the lining and in the brick Work of the high sidebelow the level of the slag line, which hole is plugged with refractory sand 11., or the like. I also refer to construct the 'ton'of the side oval lining with no appreciable ledge.

I operate the furnace as time modified the iurnacre with from two original rated capacity of scrap, anti melt the entire charge. During the initial. melting, when slag collects on the bath, interfering with the operation of the electrodes, ll thin out the slag by adding a small amount of an oxidizer, such, for example, as

iron ore, and slough oi the thinned slag by tilting the furnace. 11" the slag will not run out of the holes bored. into the scrap the electrodes, 1 make, an opening the v are, hccause the contents otthe furnace is a. more or solid mass having excellent conductivity. Thus the heavy load fluctuations incident tothe initiation of the meltin eliminated, and care need he exercise only with respect to the removal of the slag, intervals, as may he required. To this end, as before, I occasionally add an o'xi diner to thin out the slag to permit of its being readily sloughed elf. In sofa! as I I n am aware, I am the nrst to do this in this art, particularly in the acid electric process, which is" the'process I prefer,

i'Vhen the initial. charge 'l'itz: heen co1n pletely melted i draw or? only a portion of the melted chargeas the firsthatch, referahly about one half, this using pcssi le beof the increased capacity, and then I c, iantity of scrap preferably sulficient to case just supposed, about the same amount furnace. Thus total con capacity of a standsinlcs into the bath substantially solid l or compact mass of r Eatively high or ample conductivity, so than the full efiiciency of the current is obtained. Fir" the scrap should higher than the other, as shown, for era not sink freely because of slag remaining on the of molten metal left in the furnace as aforesaid, it. thru out the slag as before, sloughing ordrawinyi' it off through the interstices amen st t .e pieces of the cold recharge just adced, and thus imparting some of its heat the recharge".

lnadditi'on to the greater efficiency ob -ccharge into the remaining'molten metal a he again two to four 21 turn on the current and teined by virtue of the fact that the mass has greater conductivity, it will be apparent that current and time will be required to melt the charge because the remaining molten metal will greatly assist in melting the added charge. As before, from time to time, ll remove the slag by first thinning out; and when the charge is completely i I n melted, l again draw ofi one half and renll or recharge the furnace. This cycle of periodic recharges in ing them and drawing elf correspon inghatches, and sloughingofi sla is repeated'until the days run is completed, when the last charge is completely drained oil to permit of the repair of the lining, if

recfiiired.

fter the complete charge has been drawn off I charge the furnace while still hot with another extralarge initial charge of some 16,000 to 20,000 pounds more or less of -'scrap, and'leave it therein overnight to before stated.

"To still further increase the capacity of the standard furnace, I prefer to tilt the furnace during operation, so that it will occupya position such as shown in Figure 3,

' with its axis inclined to the vertical.

ca .tit

This enables me to take'advantage of the building up of one side of the furnace lining, a slig t tilt serving to greatly increase the pacity of the furnace. The furnace is ed to this position during the later stages of the melting of a charge, say, for example,

'- at the times when the scrap has become immersed in" the bath. I

Itwill be seen from the foregoing that I avoid the heavy load fluctuations ordinarily encountered because of the size shape and disposition of the-scrap, at all times with the possible exception of the initial melting of the first charge of the days. run, and that by thinning out and sloughing olf the slag during fusion of charges, etc., I obviate interference thereof with the passage of current 'or are between the-charge and the electrode means and the heavy load fluctuations due to that cause as well as the eating up of the electrodes normally encountered in standard practice. -I am thus enabled not only to extend the life of the electrodes from two to three times beyond what may be ordinarily expected in standard practice, but also to produce a su erior product. I am-also able to increase t e output as comared with that of an unmodified standard urnace operated in the usual manner; since i with an initial charge oftwo to four times the original rated capacity .of the furnace, a recharge even no more than half the initial charge, and a decreased duration of the fusion'process clue to the better electrical conditions, 111311 draw ofl' molten batches ladle first as. is usually. the case in standard during the process of fusion, etc.,

practice and thus no impurities areabsorbed from the slag aswould otherwise occur. This is also advantageous when ladle additions are to be made.-

I have further found in the operation of standard furnaces, of the character described, that the brick work burns-off as shown, for example, in Figure 4, and this, together with the fact that I have discovered that a much thinner lining may be em-' .ployed, enables me to still further increase the capacity of the furnace.

In constructing new furnaces to operate in accordance with my invention, I construct the same with a deep hearth as set forth and with the other requirements if desired.

*1 claim:

1. A method of,electric steel production in molten batches through periodic melting of corresponding charges by current passing between such char es and .superjacent electrode means; winch method comprises initially charging into the furnace and melting an extra large charge, and thereafter 'smaller ones; leavm in the furnace, after each batch drawn 0 during a run, enough molten metal to give. tlfe mass of the succeeding charge conductivity to sustain the flow of current between the same and the electrode means; and at the end of a run drawing off all the metal in the furnace and rechar ing-it while still hot with an extra large nitial charge for the next run, to absorb heat during the interval before such next run.

2. A method of electric steel production through melting by current passing between the charge and superjacent electrode means; which method comprises thinning and sloughing ofiz' slag durmg the process of fusion to obviate interference of such slag with passage of current between charge and electrode means.

3. A method of electric arc production of molten'steel according to the acid process; which method comprises sloughin ofi' slag during the rocess of fusion to o viate interference 0 such slag with the are. 4. A method of electric steel production inmolten batches through periodic melting of corresponding charges by current passing between such char es and" superjacent electrode means; which methodv comprises leaving in the furnace, when drawing off a batch enough molten metal to give the mass of the. succeeding charge conductivity to sustain the flow ofcurrent between the same and'the. electrode means; and sloughing or drawing off through the, interstices of such succeeding char' e slag remaining on the mciliten metal le in the furnace as aforesai 5. A method of electric steel production in molten batches. through periodic melting trode means; which :znetho comprises 31 vthe electrode moans; (laying fusion '0 of corkesponding charms by curreni pa osiiixg between such charges and super aconi; ciao in She fuwnuce, when drawing off b? o 1 enough molten meta to give the 1112.521; of mo succeeding charge conductivity to soma'm the flow of current be zweon the some, and

charges sloughing n51 resulting slag to ob Viate interference thoroof with tho flows of current between charge and electrode moan.

6. A mothoca of slocirio are produc bion of steel in molten bnichos, mom-din?" to the acid process, through periodic melting of v corresponding charges; which method comprises leaving in the X' off a baich, enough with the succeedmg nose, when flz'znving xaz'zolten metal to form. charge substantially solid mass of ample conductivity to sub-J". the are; and during ins-ion of charges thinning and sloughing ofl resulting 5121;; 50 0bviate intorfeyenoo thereof with the are.

7. A method of electric are produotioa oi' smoeedm interferes x'oxfi'nzrge with such mats, .h'mwng 01% such slog, t n misrsticos tho recharge; run dorm on all the for 1 v the and 

